Galvanizing Bolts FAQs

A wet storage stain is a white, rust-like surface discoloration that occurs from storing newly hot-dip galvanized materials. Wet storage stains occur when recently hot-dip galvanized materials are subjected to a moisture-rich environment and/or the materials are packed so closely together that there is not enough air movement and oxygen for the parts to “breathe”.... Read more

A193 Grade B7M is a grade variation of the common A193 Grade B7 used in high-temperature, high-pressure applications. Nowhere in the A193 specification does it discuss whether or not A193B7M fasteners can be galvanized. In theory, there is nothing preventing someone from galvanizing the material, however, the application in which these bolts are intended to... Read more

Yes. Portland Bolt can partially galvanize an anchor bolt. However, it is far more common for anchor bolts to be fully galvanized. If hot-dip galvanizing is required, engineers sometimes specify that only the exposed, projecting end of an anchor bolt should be galvanized, while the rest of the anchor bolt that gets embedded into concrete... Read more

A common question when deciding whether hot-dip galvanizing is an adequate corrosion resistant coating for a fastener is, “How long will the galvanizing last before the steel begins to corrode?” The last thing you want to do is install a bolt in a corrosive environment, only to have it begin to rust a year later. Unfortunately... Read more

The overtapping allowances for mechanically galvanized nuts are the same as overtapping allowances for nuts that are hot-dip galvanized. Mechanically galvanized nuts that adhere to ASTM B695 are “cold-galvanized,” which implies that they are coated with zinc at room temperature. Neither electricity (electroplate galvanizing) nor heat (hot-dip galvanizing) are applied in a mechanically galvanized process.... Read more

Can I use a mechanically galvanized nut with a hot-dip or electroplate galvanized bolt (or vice versa)?

No, mixing and matching different types of galvanized products is not advised. From ASTM A563/A307/A354 and F1554: “4.7.4 When no preference is specified, the supplier may furnish either a hot-dip zinc coating in accordance with Specification F2329, or a mechanically deposited zinc coating in accordance with Specification B695, Class 55. Threaded components (bolts and nuts)... Read more

Both are produced via the hot dip process, but with slightly different processing steps. G90 is a coating grade within the steel sheet specification ASTM A653, and is produced by uncoiling steel coils and running it at high speed through the pickling process and molten zinc before it passes through an air curtain, which creates... Read more

The answer to this question is yes! All three grades within the ASTM F1554 specification, Grade 36, Grade 55, and Grade 105, can be either hot-dip galvanized or mechanically galvanized. The issues of hydrogen embrittlement and/or mechanical properties being alerted during galvanizing are not an issue with any of these three grades. In Section 7... Read more

Mechanical galvanizing (ASTM B695) is a process in which fasteners are tumbled in a barrel with a mixture of water, zinc powder, other chemicals, and glass impact beads. As the parts are tumbled in the slurry, the zinc is “cold welded” to the fasteners. While some mechanical galvanizers can process parts that over a foot... Read more

Hot-dip galvanizing is a process of applying a protective zinc coating by dipping product in bath of molten zinc. Galvanizing is a favored method of protective coating due to its low cost, ease of application, and long maintenance-free service life. Generally applied at 830 to 870 degrees, the zinc will bond with the steel. It... Read more